CN102515561A - Preparation technology of Cu (In, al) Se2thin film - Google Patents

Abstract

The invention relates to a preparation process for a Cu(In, Al)Se2 film, comprising the following steps of: (1) preparation for target; (2) alternate sputtering deposition for Cu-In-Al at room temperature, wherein during the process, the radio of each element in a CIA prefabricated layer is controlled by controlling sputtering pressure, sputtering distance, sputtering power and different sputtering orders; (3) annealing treatment; and (4) selenylation treatment: selenylation treatment is performed on the annealed prefabricated layer, and a Cu(In, Al)Se2 polycrystalline film with a chalcopyrite structure is formed via selenylation in Se atmosphere. In the preparation process disclosed by the invention, CIA prefabricated layer is obtained by sputtering deposition at room temperature, and then is subjected to annealing treatment and selenylation treatment, so as to obtain Cu(In, Al)Se2 polycrystalline film with chalcopyrite structure; moreover, the costs of preparation for target and magnetron sputtering equipment are saved, so that the preparation cost of Cu(In, Al)Se2 film is greatly decreased.

Description

Preparation Technology of Cu(In,Al)Se2 Thin Film

technical field

The invention relates to thin film materials, in particular to a preparation process of copper indium aluminum selenium Cu(In, Al) _Se2 thin film.

Background technique

Copper indium selenide (CuInSe ₂ ) thin film solar cells have attracted much attention due to their better optical energy gap (Eg), high absorption rate (10 ⁵ /cm), strong radiation resistance and long-term stable performance. Its production is also becoming industrialized, so how to reduce production costs and improve the conversion efficiency of batteries has become the focus of research.

Among them, the material of the absorbing layer is a key factor affecting the photoelectric conversion rate of the battery. The study found that by partially replacing In with Ga and Al for adjustment, a wider band gap and a higher solar spectrum matching degree can be obtained. The doping of Al element makes the forbidden band width of CuInSe ₂ type solar cells have a wider range than that of Ga-doped solar cells, and the corresponding Eg variation range is 1.0-2.7eV. Therefore, the Cu(In, Al)Se ₂ film also has the function of improving the performance of CuInSe ₂ type solar cells. Cu(In, Al)Se ₂ with a wide Eg variation range can use the same material to make Cu(In, Al)Se ₂ films that absorb light of various energies by controlling the proportion of aluminum in the film, so that Improve the absorption efficiency of the battery, but also reduce the cost of materials. Here, Al is used to partially replace In to form a Cu(In, Al)Se ₂ miscible crystal material.

At present, most CuInSe ₂ and Cu(In, Al)Se ₂ thin films are prepared by vacuum evaporation or magnetron sputtering deposition of CuInAl (CIA for short) pre-layer and selenization under the condition of substrate heating. The film layer is prepared by heating the substrate, which has relatively high requirements on the magnetron sputtering equipment. It needs to be equipped with a special substrate heater and temperature control system, which increases the investment in equipment.

Contents of the invention

In view of the deficiencies in the prior art, the present invention provides a new preparation process of Cu(In, Al) _Se2 film through process adjustment.

Technical solution of the present invention is realized like this:

A kind of Cu (In, Al) Se The preparation technology of _thin film, comprises the steps:

(1) Preparation of the target: prepare a pure Cu target and an InAl composite target respectively, the InAl composite target is obtained by inlaying In blocks of different areas on the Al target, In/Al=5-20%;

(2) Cu-In-Al alternate sputtering deposition at room temperature: At room temperature, Cu, In, and Al are alternately sputtered and deposited on the glass substrate by DC magnetron sputtering to form a CuInAl prefabricated layer, wherein the alternate sputtering The order of sputtering is first Cu target and then InAl target, so repeat sputtering several times, the total sputtering time is not less than 45min; background vacuum degree is 1.5x10 ^-2 ~ 2.5x10 ^-2 Pa; Cu target sputtering power is 160 ~ 300W; InAl target sputtering power 170~400W; nitrogen or argon gas pressure 2x10 ^-1 -5x10 ^-1 Pa;

(3) Annealing treatment: the CuInAl prefabricated layer is placed in a selenization furnace for vacuum annealing at 400-600°C;

(4) Selenization treatment: perform selenization treatment on the annealed prefabricated layer, and form a Cu(In, Al)Se ₂ polycrystalline thin film with a chalcopyrite structure by selenization in Se atmosphere.

Further, in step (2), the Cu target sputtering power is 180-260W; the InAl target sputtering power is 230-350W. the

The present invention does not use substrate heating in the process of magnetron sputtering to prepare the CuInAl preset layer, but adopts the normal temperature sputtering deposition method; especially, in terms of target material utilization, pure Cu targets and InAl composite targets are used , the InAl composite target is obtained by embedding In blocks of different areas on the Al target; furthermore, during the Cu-In-Al alternate sputtering deposition process, considering the distribution of the magnetic force lines of the non-equilibrium magnetic field, Al and In have different The sputtering rate and the uniformity of the target sputtering, by controlling the sputtering sequence and sputtering parameters, changing the area of the InAl composite target to prepare CuInAl pre-layer films with different atomic ratios of Cu, In, and Al, where Cu:( In+Al)=0.5~2, Al: (In+Al)=0.1~0.9; then the CuInAl prefabricated layer is annealed and selenized to prepare Cu(In,Al)Se ₂ polycrystalline chalcopyrite structure film. On the one hand, this method saves the cost in the preparation of the target, and on the other hand saves the cost of purchasing or refitting the magnetron sputtering equipment, so that the preparation cost of Cu(In, Al)Se ₂ film is greatly reduced.

Description of drawings

Fig. 1 is the surface topography figure (10000x) before and after the annealing of CIA prefabricated layer film; Wherein,

Fig. 1 (a) is the surface topography figure when not heat-treated;

Figures 1(b)~1(d) are the surface topography images annealed at 450°C, 500°C and 550°C, respectively;

Figure 2 is the XRD pattern of the CIA prefabricated film without annealing, annealing at 450°C and 550°C;

Fig. 3 is after annealing, before selenization CIA prefabricated layer and Cu (In, Al) Se after _selenization Surface topography figure (10000x) of thin film; Wherein,

Fig. 3 (a) is the surface topography figure of the CIA prefabricated layer film before selenization;

Figures 3(b) to 3(d) are the surface topography diagrams of Cu(In, Al)Se ₂ films selenized at a selenium source temperature of 250°C and a substrate temperature of 400°C, 450°C and 500°C, respectively;

Fig. 4 is an XRD pattern of Cu(In, Al)Se ₂ thin films at different substrate heating temperatures.

Detailed ways

A kind of Cu (In, Al) Se The preparation technology of _thin film, comprises the steps:

(1) Prepare the target material: prepare a pure Cu target and an InAl composite target respectively, the InAl composite target is obtained by inlaying In blocks of different areas on the Al target, In/Al=5-20%;

(2) The CIA prefabricated layer was deposited by alternating sputtering at room temperature by DC magnetron sputtering method, the process is simple and the elemental composition is easy to control. That is, the proportion of each element in the CIA prefabricated layer is controlled by controlling the sputtering pressure, sputtering distance, sputtering power, and different sputtering sequences; the targets used in the magnetron sputtering in the present invention are Cu targets and InAl composite targets. CuInAl prefabricated films with different InAl atomic ratios can be prepared by changing the area ratio of the InAl composite target; wherein, the distance between the substrate and the target is 50-100 mm; the order of alternate sputtering is first Cu target and then InAl target , so repeated sputtering several times, the total sputtering time is not less than 45min; background vacuum is 1.5x10 ^-2 ~ 2.5x10 ^-2 Pa; Cu target sputtering power 160 ~ 300W; InAl target sputtering power 170 ~ 400W; The pressure of nitrogen or argon is 2x10 ^-1 -5x10 ^-1 Pa;

(3) Anneal the CIA prefabricated layers of different components deposited at room temperature in a selenization furnace: heat treat the prefabricated layers at 450-550°C;

(4) Selenizing the annealed prefabricated film in a selenization furnace to form a Cu(In, Al)Se ₂ film by selenization in a Se atmosphere. In this process, the selenium source is first heated to 250° C. for 30 minutes, and then the substrate is heated to 400-500° C. for 60 minutes. Finally, the samples were cooled to room temperature with the furnace.

Table 1 lists the changes in the composition of the CIA prefabricated layer film before and after annealing under the condition of vacuum annealing at 450°C by energy spectrum analysis. It can be seen from Table 1 that after the CIA prefabricated film is heat-treated, the composition ratio of each element changes. The content of Cu in the CIA prefabricated film has increased, the content of Al has increased, and the content of In has decreased. This is because the melting point of In is only 156.6°C, which is much lower than the vacuum annealing temperature; that is, part of In is evaporated during heat treatment, which reduces the In content of the CIA prefabricated film. the

Table 1 The composition comparison (atomic percentage) of the sample before and after annealing

The samples were subjected to vacuum annealing at 450°C, 500°C, and 550°C for 45 minutes in a selenization furnace, respectively. The SEM image of sample Y15 is shown in Figure 1. It can be seen from the figure that the surface of the CIA prefabricated film without vacuum annealing is smooth and dense, and almost no particles appear, as shown in Figure 1(a); after annealing at 450 °C, the surface of the CIA prefabricated film has fine white particles, As shown in Figure 1(b); after annealing at 500°C, white granular substances appeared on the surface of the CIA prefabricated layer film, and fine cracks appeared on the surface of the prefabricated layer, as shown in Fig. 1(c); 550°C annealing treatment After that, the number of white particles increased even more, as shown in Figure 1(d). Experiments have shown that after vacuum annealing, obvious white granular substances appear on the surface of the CIA prefabricated layer film. After EDS micro-area analysis, these white granular substances are indium-rich phases. This is because after the annealing treatment, In reacts with Cu atoms to form a Cu-In alloy, and the melting point of In is low. In the CIA prefabricated film, In is easier to precipitate first, so the white particles on the surface of the CIA prefabricated film have In. Enrichment. the

The structure of the CIA prefabricated layer changed after vacuum annealing, as shown in Figure 2. The non-annealed CIA prefabricated film is amorphous and has no obvious peak, but after vacuum annealing at 500℃ and 550℃, the CIA prefabricated film appears Cu-In alloy Cu11In ₉ and CuIn phases. This shows that the CIA prefabricated layer crystallized after the annealing treatment, and preferentially grew in the (11-1) direction. It can also be seen from Figure 3 that the crystallinity of the CIA prefabricated layer increases with the increase of the annealing temperature. Except for a small amount of In which did not react, the rest all formed Cu11In ₉ and CuIn alloys. And no diffraction peaks of Al single substance were observed in the XRD diffraction pattern, which indicated that the substrate temperature was normal temperature and the CIA prefabricated layer film was annealed, and the position of Al in the film layer replaced part of In and formed an alloy with Cu. Therefore, the vacuum annealing of the CIA prefabricated layer can promote the diffusion and recrystallization of Cu, In, and Al atoms in the film layer, so that Cu, In, and Al can be effectively combined.

The CIA prefabricated layer after heat treatment at 450°C was subjected to selenization treatment, wherein the selenization temperature was 250°C, kept for 30 minutes, the substrate heating temperatures were 400°C, 450°C, 500°C, and the holding time was 60 minutes to obtain Cu(In, The surface morphology of the Al) _Se2 thin film is shown in Fig. 3. It can be seen from Figure 3(a) that there are a large number of fine white particles on the surface of the CIA prefabricated layer after heat treatment, and the surface of the Cu(In,Al) _Se2 film in Figure 3(b) is mainly elongated or flaky Particles, as shown in Figure 3(c), there are large particles agglomerated on the surface, indicating that the selenization is not complete. Figure 3(d) The surface of the sample is obviously granulated. It shows that the CIA prefabricated layer reacts more fully with the Cu-In-Al element in the sample as the selenization annealing temperature rises.

From the XRD pattern of the Cu(In, Al)Se ₂ thin film before and after selenization, as shown in Figure 4, it can be seen that the CIA prefabricated film without heat treatment does not have obvious diffraction peaks, and is amorphous or microcrystalline. After selenization treatment, there are obvious diffraction peaks in the XRD diffraction spectrum, and the growth is preferential in the (112) direction, maintaining the chalcopyrite crystal structure. With the increase of annealing temperature, the diffraction peak along the (112) direction is enhanced.

That is, annealing can promote the diffusion and recrystallization of atoms in the CIA preform layer deposited at room temperature. After the annealing treatment of the prefabricated film, an indium-rich CuIn alloy phase appears on the surface, and Al partially replaces the lattice position of In, so that the lattice constant of CuIn decreases. The Cu(In, Al)Se ₂ absorbing layer with chalcopyrite structure can also be obtained after the alloyed prefabricated layer film is selenized. The XRD analysis shows that the Cu(In, Al)Se ₂ phase, which is mainly formed in the Cu(In, Al)Se ₂ film, grows preferentially in the (112) direction.

The above is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Anyone familiar with the technical field within the technical scope disclosed in the present invention, according to the technical solution of the present invention Any equivalent replacement or change of the inventive concepts thereof shall fall within the protection scope of the present invention. the

Claims (2)

1. Cu (In, Al) Se₂The preparation process of the film comprises the following steps:

(1) preparing a target material: respectively preparing a pure Cu target and an InAl composite target, wherein the InAl composite target is obtained by inlaying In blocks with different areas on an Al target, and the In/Al ratio is 5-20%;

(2) room temperature Cu-In-Al alternate sputtering deposition: at room temperature, alternately sputtering and depositing Cu, In and Al on a glass substrate by adopting a direct-current magnetron sputtering method to form a CuInAl prefabricated layer; in the process, the sputtering pressure, the sputtering distance, the sputtering power and the difference are controlledThe sputtering sequence of the CIA prefabricated layer controls the proportion of each element in the CIA prefabricated layer; wherein the distance between the substrate and the target is 50-100 mm; the sequence of alternate sputtering is that Cu targets are firstly sputtered and then InAl targets are sputtered repeatedly, and the total sputtering time is not less than 45 min; background vacuum of 1.5X10^-2～2.5x10^-2Pa; the Cu target sputtering power is 160-300W; the InAl target sputtering power is 170-400W; the pressure of nitrogen or argon is 2x10^-1-5x10^-1Pa；

(3) Annealing treatment: the CuInAl prefabricated layer is placed in a selenizing furnace and subjected to vacuum annealing at the temperature of 400-600 ℃;

(4) selenylation treatment: selenizing the annealed prefabricated layer In Se atmosphere to form Cu (In, Al) Se with a chalcopyrite structure₂A polycrystalline thin film.

2. Cu (In, Al) Se according to claim 1₂The preparation process of the film is characterized by comprising the following steps:

in the step (2), the Cu target sputtering power is 180-260W; the InAl target sputtering power is 230-350W.

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